A number of factors have been previously reported to be associated with high risk of malignant melanoma. These include age, sex, race, ethnic origin, complexion, ability to tan, hair color, eye color, and sun exposure. A case-control study has been designed to determine the degree of association between the occurrence of malignant melanoma and possible risk factors, including some which have not received quantitative analysis previously. The total data base willconsist of approximately 1100 cases and a similar number of controls. Cases are being drawn from the tumor registry of the NYU Skin and Cancer Unit, whereas controls are randomly selected from the NYU Skin and Cancer Unit patients without melanoma or other neoplastic conditions. It is hoped that this study will lead to the identification of high risk groups at whom future monitoring for malignant melanoma could be directed. Significant positive associations found in the study, if corroborated by others, may also identify behavior patterns, which, if modified, could result in a decreased incidence of the disease.